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United States Patent | 5,045,715 |
Fitch | September 3, 1991 |
A clock circuit for generating two clock signals, one (CLK) having stretched clock phases on a cycle by cycle basis, and the second (2X CLK) being a clock signal having a frequency twice the frequency of the first clock signal which is phase and edge coherent with the first clock signal, including the stretched clock phases. The circuit inputs a signal generated by an oscillator which is twice the frequency of the CLK signal which is then used to generate the CLK signal for use by a microprocessor, either phase of which can be stretched on demand, while the second 2X CLK signal remains phase coherent with the microprocessor CLK signal.
Inventors: | Fitch; Jonathan M. (Cupertino, CA) |
Assignee: | Apple Computer, Inc. (Cupertino, CA) |
Appl. No.: | 495329 |
Filed: | March 19, 1990 |
Current U.S. Class: | 327/174; 327/116; 327/141; 327/163; 327/176; 327/216; 377/47 |
Intern'l Class: | H03K 003/02; H03K 003/64; H03K 005/13; H03L 007/085 |
Field of Search: | 328/58,60,62,63,72,155,20,15 307/262,267,269,480,271 377/47 |
4604582 | Aug., 1986 | Strenkowski et al. | 328/63. |
4691170 | Sep., 1987 | Riley | 377/47. |